The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and designs have produced generations of ICs, and each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. Although the existing semiconductor devices and the forming methods thereof have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.